The present invention relates to a technology for recording and playing back signals such as video and audio signals into and from an erasable recording medium such as an optical magnetic disc, a variable phase disc and a magnetic disc.
By virtue of development of band compression technologies represented by the recently introduced MPEG (Moving Picture Experts Group) compression/coding technology, signals such as audio and video signals can now be recorded into a large capacity recording medium such as an optical magnetic disc for a playback operation of a long time.
When a signal is recorded into such a recording medium, the signal undergoes a band compression/coding process, being recorded in sector units. The signal is then recorded into free areas on the recording medium.
Traditionally, a signal continuous in the time axis direction resulting from typically editing work such as an audio or video signal is recorded into a recording medium, being split into segments as shown in FIG. 21(1). In the figure, the symbol # on each of the segments indicates the order number in an operation to play back the signal. While the segments of the signal are arranged along a straight line as shown in the figure, the signal is actually recorded on a track having a spiral shape or concentric tracks on the recording medium.
Consider a playback operation in which segment #5 is reproduced after segment #4. In this case, a reproduced signal generated by a read pickup is broken due to a seek time, a rotation wait time and a settle time which are required between segments #4 and #5. The seek time is a period of time it takes to move the read pickup in a so-called track jump to a track in area where segment #5 is recorded. On the other hand, the rotation wait time is a period of time it takes to wait for the read pickup to arrive at the position of a target sector on the track. Finally, the settle time is a period of time it takes the tracking servo of the read pickup to get settled.
In order to prevent a playback signal eventually generated by the recording/playback apparatus from being broken even if the reproduced signal generated by the read pickup is unavoidably broken as described above, a read buffer memory is provided for storing in advance a signal read out from the recording medium. The signal stored in the read buffer memory is used for filling up the time gap between two consecutive segments, that is, a period of time during which no reproduced signal is generated by the read pickup. The signal stored in the read buffer memory is then output when the reproduced signal generated by the read pickup is broken.
In-the case of a recorded signal split into a large number of segments as shown in FIG. 21(2), however, it is quite within the bounds of possibility that the amount of data stored in advance in the read buffer memory during the time is not large enough to be used for filling up a time gap between two consecutive segments. As a result, the eventual playback signal can not be generated continuously.